This invention relates to a new and improved apparatus process for producing non linear shapes from woven graphite fabric. These non linear fabric shapes are then impregnated wit resin, cured and then usually machined to form products that may be used for rocket exit cones, rocket motors, and other components for rockets, and so forth. Other curved objects such as round tank bodies, etc., also may be manufactured by the process and apparatus of this invention.
Many publications have disclosed various techniques for producing exit cones for rockets from woven graphite fabric. Typical patents in this technology include: U.S. Pat. Nos. 497,579; 1,057,085; 2,771,659; 2,884,015; 3,272,672; 3,331,402; 3,707,996; 3,719,210; 4,252,154; 4,359,190; 4,467,838; and, 4,495,231. Foreign patents include: European Patent 0,044,760 A1; French Patent 1,069,282; and Japanese Patent 47-36227.
Some of the aforesaid patents disclose products which have inherent weaknesses, such as those processes which apply fitted fabric portions onto a non uniform mandrel, such as described U.S. Pat. No. 4,359,190. Other patents disclose the use of complicated equipment (U.S. Pat. No. 3,719,210). Still other patents disclose the application of a uniform weave employing relatively simple equipment, but the fabric is applied to a uniform mandrel (Japanese Patent 47-36227). Other patents disclose the application of a single fiber onto a rotating mandrel, but this technique is primarily a unidirectional form of reinforcement (European Patent 0,044,760 A1 and U.S. Pat. No. 3,272,672).
U.S. Pat. No. 4,495,231 discloses winding up a woven fabric over a non linear mandrel for use as a rocket tail cone. This technique, however, provides no mechanism for compensating between the difference of the fabric sheet which is linear, and the non linear mandrel. Consequently, the fabric will become distorted when it is built up on the rotating mandrel.
To a certain extent, problems concerning catastrophic failure of a rocket tail cone during launch can be overcome by building an exit cone having a thick wall for the conical portion. However, since the conical portion is the heaviest part of the exit cone, this adds considerable weight to the system. Consequently, either the range of the rocket becomes limited, or more fuel is required for launching, thereby imposing restrictions on the rocket design. Also, a heavy exit cone makes it difficult to site and handle the rocket prior to launch, and transporting the device also is difficult.
It would be preferred to produce an exit cone having conical wall thickness of about 1/4 inch, or greater, while improving its tensile properties and structural characteristics. Moreover, if the usual conical wall thickness could be replaced by machining down to this 1/4 inch thickness, the weight of the exit cone could be reduced greatly, and this would be extremely useful, particularly if the structural integrity and weight requirements were improved. A desireable process would produce exit cones of up to say, 6 feet in diameter, and up to about 8 feet long.
Also, it would be desireable to produce a uniform transition between the cylinder portion and the conical portion and air the same time conform the junction between the conical and cylinder portions to a desired shape.
In addition, a process for producing an exit cone is desired that would allow the fabricator the option of whether or not pressure should be applied to the wrapped fabric prior to the resin cure stage.